Much active research in recent years has been devoted to preparations for transdermal or transmucosal administration, because of the advantages of absorption of drugs through the skin or mucous membranes of mammals, particularly humans, as compared with oral administration, from the viewpoint of easier administration, maintenance of blood levels and the ability to avoid side effects of drugs in the alimentary tract. Iontophoresis is one area which has received much attention as an effective method for local administration which accelerates absorption of drugs through the skin or mucous membranes.
Iontophoresis is a type of method for accelerating physical absorption of drugs whereby a voltage is applied to the skin or mucous membrane to induce electrical migration of the drug, for administration of the drug through the skin or mucous membrane.
Iontophoresis apparatuses consist largely of a power source apparatus which generates a current, and an iontophoresis device structure which includes an electrode layer for attachment to the skin or mucous membrane. Normally, an iontophoresis device structure is separated into a donor electrode which includes the drug, and a reference electrode. The iontophoresis which delivers the drug through the skin or mucous membrane is accomplished by forming a single electrical circuit with the power source, the iontophoresis device structure and the body and running a current through this circuit for electrical driving.
Connection between the electrode layer of the iontophoresis device structure and the power source is achieved using a snap-type protruding terminal such as disclosed in Japanese Laid-open Patent Publication No. 504343 of 1991 or Japanese Laid-open Patent Publication No. 196644 of 1996.
A conventional iontophoresis device structure will now be explained with reference to the attached drawings.
FIG. 7 is a cross-sectional schematic view of a conventional iontophoresis device structure, and FIG. 8 is a cross-sectional schematic view of another conventional iontophoresis device structure.
Here, 20 is the conventional iontophoresis device structure, 21 is a support formed into a cup shape, 22 is an electrolyte layer fitted into the concave part of the support 21, 23 and 24 are snap-type protruding terminals, 25 is an electrode layer electrically connected to the protruding terminal 24, and 26 is a separator laminated in a freely releasable manner on the rim around the opening of the concave part of the support 21.
The method of electrification for the above-mentioned iontophoresis device structure having this construction will now be explained.
In the structure illustrated in FIG. 7, the flat section under the protruding terminal 23 is contacted with the electrolyte layer 22 for use as the electrode layer, and the protruding part is connected with an external power source for electrification.
In the structure illustrated in FIG. 8, the bottom surface of the protruding terminal 24 is contacted with a separately provided electrode layer 25 for electrical connection, and the protruding part is connected with an external electrode for electrification through the electrode layer 25 which has a wide area.
These conventional iontophoresis device structures have had the following problems, however. Specifically,
(1) An insertion hole must be formed for the protruding terminal in order to project its protruding part through the bottom of the concave part of the cup-shaped support and an anchoring ring called a collar must be fitted to anchor the protruding terminal, thus requiring more working steps and reducing productivity, complicating mass production and raising costs.
(2) Leakage of the electrolyte or solvent such as water in the electrolyte layer from the insertion hole impairs the quality and lowers product yields.
(3) Because a non-flexible convex terminal is used as the snap-type protruding terminal, when the area of the underside of the terminal is widened to increase the contact between the convex terminal and the electrolyte layer in the case of the structure shown in FIG. 7, the contouring is poorer upon attachment to the body, while conversely if the underside of the terminal is reduced, a current flows directly under the lower end of the terminal, resulting in greater danger of electrical irritation to the body and lower safety.
(4) When a separate electrode layer is provided as shown in FIG. 8, it is necessary to carry out an integrating step for the more complex convex terminal as well as for the electrode layer, and thus working efficiency is reduced, productivity is impeded, and costs are increased.
(5) Although some structures employ silver or silver chloride in an ABS resin as the material for the convex terminal, and other structures have nickel platings on zinc, when ABS resins are used the terminal must be formed to a prescribed thickness to provide strength for the convex terminal, and hence there is a limit to how thin the thickness of the lower end of the terminal can be made. Also, structures wherein zinc is covered with a nickel plating, etc., have the problem of elution of the zinc or nickel, etc., by the electrolyte reaction upon electrification, so that the safety is poorer.
(6) When the protruding terminal is connected with the external power source, excessive pressure on the protruding terminal may break the iontophoresis device structure and cause leakage of its contents, such as the electrolyte layer.
(7) Because the rim of the protruding terminal is round, the connector is prone to detachment during electrification by the external power source.
The present invention overcomes these problems by providing an iontophoresis device structure which has excellent contouring ability at its site of attachment, has very high safety, is of high quality with high product yields, and can be produced with fewer production steps to improve working efficiency and increase productivity to allow mass production at low cost.